Blowout preventer with variable inside diameter

ABSTRACT

A variable inside diameter blowout preventer capable of sealing off a bore or around an object against high well pressures, and which may be either a ram-type preventer or an annular preventer, and wherein a plurality of upper and lower anti-extrusion members are each disposed in two overlapping layers and are mounted for radial movement to and from a sealing position and an open position, with the anti-extrusion members inhibiting extrusion of a resilient sealing member therewith throughout a predetermined range of variable inside diameters of the sealing member and anti-extrusion members.

United States Patent LeRouax *Oct. 28, 1975 BLOWOUT PREVENTER WITHVARIABLE 2,368,928 2/1949 King 166/10 INSIDE DIAMETER 2,609,836 9/1952Knox 277/73 2,780,294 2/l957 Lo0mis.... l66/203 Inventor: Robert oHouston. 2,846,178 8/1958 Minor 251/229 x 3,038,542 6/1962 L0omis....166/204 [73] Asslgnee' Company 3,572,628 3/1971 Jones 251/1 Notice: Theportion of the term of this Patent Subequ9m to y 29, 1992 PrimaryExaminer-Martin P. Schwadron has been dlsclalmed' AssistantExaminer-Richard Gerard 2 Filed; 5, 1973 Attorney, Agent, or FirmPravel& Wilson [2]] Appl. No.: 412,771 ABSTRACT 57 Related US. ApplicationData 1 [63] Continuationin a t f S N 326 965 J 26 A var1able 1ns1ded1ameter blowout preventer capable 1973 abandon-g r 0 of sealing off abore or around an object against high well pressures, and which may beeither a ram-type 52 US. Cl 251/1- 277/127 Prevent an annular Prevent",and wherein [51] Int. Cl. E21B 33/06 rality of upper and loweranti-extrusion members are [58] Field Of Search 251 /1; 277/73, 126,127, each disposed in verlappmg layers and are 277/129 181 185 188166/81 82 84 mounted for radial movement to and from a sealing positionand an open position, with the anti-extrusion members inhibitingextrusion of a resilient sealing [56] References Cited member therewiththroughout a predetermined range of variable inside diameters of thesealing member and UNITED STATES PATENTS anti-extrusion members.2,035,925 3/1936 Seamark 277/34 2,246,709 6/1941 Allen 277/129 11Claims, 10 Drawing Figures US. Patent Oct. 28, 1975 Sheet 1 of 4 Sheet 2of 4 3,915,426

US. Patent Oct. 28, 1975 U.S. Patent Oct. 28, 1975 Sheet 3 of4 3,915,426

US. Patent Oct. 28, 1975 Sheet 4 of4 3,915,426

BLOWOUT PREVENTER WITH VARIABLE INSIDE DIAMETER CROSS-REFERENCE TORELATED APPLICATIONS This application is a continuation-in-part of U.S.patent application Ser. No. 326,965 filed Jan. 26, 1973, copendingherewith, and now abandoned.

BACKGROUND OF THE INVENTION The field of this invention is blowoutpreventers for oil wells and the like.

Annular blowout preventers made by the Hydril Company, an example ofwhich is shown on page 2742 of the Composite Catalog for 1970-71, havebeen in extensive commercial use for a number of years. Such blowoutpreventers provide a fully-open bore therethrough so that drill bits,reamers, casing hangers and other large diameter tools can freely passtherethrough, but when actuated to the closed position, the packing ofeach such preventer is forced inwardly to reduce its bore andautomatically adjust its size and shape in sealing contact with whateverobject happens to then be in the bore of the preventer, thereby closingoff the annular space around such object to prevent a blowout of wellpressure from below. If no tool is in the well, the bore of thepreventer can be fully closed to prevent a blowout.

Although such Hydril blowout preventers are very satisfactory forrelatively low well pressures in the range of from about 2,000 psi. to5,000 p.s.i., it is generally desirable to use a ram type blowoutpreventer above such pressures, and above 10,000 psi. well pressure, ithas heretofore been considered essential to use a ram type blowoutpreventer of a predetermined opening size because of the inability tosatisfactorily prevent extrusion of the rubber of the preventers at suchhigher pressures.

SUMMARY OF THE INVENTION The present invention relates to blowoutpreventers wherein a resilient sealing member or members are providedfor closing a well bore or sealing with a pipe or other object disposedin the bore and wherein antiextrusion means are mounted with the sealingmember or members to prevent extrusion thereof over a' relatively largevariable range of bore diamters for the preventer, and wherein theblowout preventers of this invention may be of the ram type or theannular type, and are yet capable of sealing off much higher wellpressures than with prior known annular blowout preventers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, is a vertical sectional viewillustrating one embodiment of the blowout preventer of this inventionin the retracted or opened position;

FIG. 2 is a view similar to that of FIG. 1 illustrating the blowoutpreventer in the closed or sealing position with a pipe in the wellbore;

FIG. 3 is a view taken on line 33 of FIG. 1 to illustrate in particularthe anti-extrusion means of the blowout preventer of this invention;

FIG. 4 is a view taken on line 44 to further illustrate theanti-extrusion means of FIG. 3 when in the contracted position with thesealing means in sealing contact with the well pipe;

FIG. 5 is a view taken online 5-5 of FIG. 3;

FIG. 5A is a view taken on line 5ASA of FIG. 4;

FIG. 6 is an isometric view of the upper antiextrusion means used withthe blowout preventer of this invention in the annular or cylindricalform thereof;

FIG, 7 is a vertical sectional view of the blowout preventer of thisinvention in the ram type preventer;

FIG. 8 is a view taken on line 88 and illustrating a portion of theblowout preventer of this invention in the ram type; and

FIG. 9 is an isometric view, partly exploded, illustrating the upperanti-extrusion means used with the ram type blowout preventer of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, the letter Brefers generally to the form of the blowout preventer of this inventionshown in FIGS. l6.

Briefly, the preventer B includes a housing H which has a centrallongitudinal bore 10 through which a pipe P or other object is adaptedto extend in the known manner for well operations. The housing H isconstructed so that it is positioned in a stack of blowout preventers orin a string of well casing or pipe in any suitable manner, as will beunderstood by those skilled in the art. The blowout preventer B has areplaceable assembly A, the details of which will be describedhereinafter, which has a central bore 11 which is preferably at least aslarge as the central opening or bore 10 and which is likewisesubstantially the same size or at least as large as the bore of thecasing or pipe above and below the preventer B so that a full openingbore 11 is available for the passage of the pipe P and other well toolsduring normal operations.

Considering the details of the blowout preventer B,

the housing Hmay take numerous forms, but as illus-' trated in thedrawings, it includes a lower housing section 12 having a housing recess12a for receiving the blowout preventer assembly A and an annular piston14 formed of rubber or similar material, as will be further explained.The recess 12a is further defined by a housing section or cover 15 whichis secured to the housing section 12 by bolts 15a (FIG. 1) or othersuitable securing means. A fluid line 12b and a fluid relief line 15bcommunicates through the housing H with the recess 12a for the inlet andrelief of hydraulic or other fluid pressure with respect to theresilient piston 14 to control the opening and closing of the blowoutpreventer B, as will be more evident hereinafter. For connecting thehousing H in a stack of blowout preventers, or to suitable flanges ofthe well pipe or casing above and below the blowout preventer B,connecting threaded studs 12c and 150 are preferably provided, althoughany other suitable connecting means may be employed. Connecting studs150 are preferably dis- I posed longitudinally in alignment with theconnecting means M is also provided with the seal member 30, as will bemore fully explained. The upper anti-extrusion means M is preferablyidentical to the lower antiextrusion means M in the preferred form ofthe invention, except that they are upside down with respect to eachother. Therefore, the details of the anti-extrusion means M will behereinafter explained and the same parts will be identified with thesame numerals and/or letters followed by a prime mark for the lowerantiextrusion means M.

The upper anti-extrusion means M is illustrated in detail in FIGS. 3-6.Such anti-extrusion means M includes an upper or first set ofanti-extrusion members 35 which together form an annular or cylindricalassembly (FIG. 6). In fact, the members 35 may be cut or otherwiseformed from a single solid cylindrical member or ring. The radial edgesor sides 35a of each of the members or segments 35 are disposed radiallyand if extended would all converge at a single point in the center ofthe bore or opening defined by such segments 35. The inner surfaces 35bof the segments or members 35 form the inner bore of the upper or firstset of the antiextrusion members 35, which bore may vary from itssmallest diameter (FIG. 6) to a larger retracted diameter (FIGS. 1 and3).

The outer surface 35c of each of the members or segments 35 is likewiseformed in a cylindrical surface with the other surfaces 350 and in thepreferred form of the invention, a pair of threaded openings 35d areprovided in such surface 350 of each segment 35 for a purpose to behereinafter explained.

The upper anti-extrusion means M also includes a second or lower set ofanti-extrusion members or segments 36 which are likewise formed in asubstantially cylindrical or annular shape as a ring when assembled intheir innermost contracted position (FIG. 6) and which are adapted tomove outwardly to a larger inner bore diameter as shown in FIGS. 1 and3. The members 36 are staggered or are spaced alternately with respectto the members 35 so that the radial edges 35a of the segments 35 aredisposed substantially midway of the segments or members 36 when thesegments 35 are in their retracted position of FIG. 6. The sides oredges 36a of the segments 36 extend substantially radially although theyare also preferably inclined as shown in the drawings since thelowermost surface 36d of each segment 36 is bonded or is otherwisesecured to the rubber or other material of the sealing element 30, andsuch inclined surfaces 36a provides room for some distortion of therubber of the sealing element 30 without binding the movements of themembers 36. The inner surfaces 36b of the segments 36 are preferablydisposed coextensively with the surfaces 35b so as to form a bore whichis of the same diameter as the bore formed by the surfaces 35b. Also, aswill be explained, the surfaces 35b and 36b remain vertically alignedduring the radial movement of the segments 35 and 36 from the openposition to the closed position of the blowout preventer B and viceversa. Each of the segments 36 has an outer surface 36c which is formedwith one or more openings 36e, the purpose of which will be hereinafterexplained.

The segments 35 and 36 are connected together so that they may moveradially from the enlarged or retracted position of FIGS. 1 and 3 to themaximum closed position of FIGS. 4 and 6 by connectors 40. Eachconnector 40 also serves to prevent extrusion of the ring 14 and/or thesealing member 30 radially and horizontally between the edges 35a ofadjacent segments 35. Each connector 40 is secured to one of thesegments 36 by a screw or other fastener 41 which extends into thethreaded opening 36e. Each connector 40 is connected to a pair ofsegments or anti-extrusion members 35 disposed above the segment 36 withwhich the connector 40 is secured, by a slidable connection whichincludes lateral or circumferential slots 40a in the connector 40through which connector screws or pins 42 are disposed. Each connectorpin 42 extends into one of the openings 35d on the outer surface of oneof the segments 35, and each pin 42 has a head 42a which is larger thanthe slot 40a so that the segments 35 are forced to move radially withthe segments 36 while permitting relative circumferential movements ofthe members 35 with respect to the member 36 with which it is connected,within the limits provided by the length of the slots 40a.

In the operation or use of the blowout preventer B of FIGS. 1-6 of thisinvention, the normal undistorted shape of the sealing member 30 isillustrated in FIG. 1 and in that position, the segments 35 arecircumferentially spaced from each other so that there is a spacebetween the sides 35a of the adjacent segments 35. The segments 36 belowthe segments 35 cover the gap thus present between the edges 35a of thesegments 35 and prevent extrusion of rubber upwardly into the spacesbetween the segments 35. When it is desired to seal with the pipe P orother object in the well bore, hydraulic pressure or the like isintroduced through the line 12b to urge the annular piston 14 inwardlyto thus force the sealing element 30 into a smaller diameter and finallyinto sealing contact with the external surface of the pipe P. Duringsuch inward distortion of the sealing element 30 to its sealing positionwith the pipe P, the segments 36 are carried with the rubber or othermaterial of the sealing element 30 and they thus move radially inwardlyto reduce the inner bore diameter of the inner surfaces 36b until theyengage the pipe P. The connectors 40 urge the segments 35 radiallyinwardly with the segments 36 and permit them to move closer to eachother to close the gap between their side edges 35a until the surfaces35b engage the pipe P also. It will be understood that the surfaces 35band 36b remain substantially vertically aligned at all times andnormally are also substantially vertically aligned with the inner bore30a of the sealing member or element 30 so that extrustion of thesealing element 30 longitudinally of the pipe P is prevented by theoverlapping segments 35 and 36 at all times.

The lower anti-extension means M has segments 35' and 36 whichcorrespond with the segments 35 and 36 and they are connected togetherby connectors 40' in 55 the same manner as the connectors 40 serve toconnect the segments 35 and 36 as previously explained. The loweranti-extrusion means M functions in the same manner as the upperanti-extrusion means M and both work simultaneously above and below thesealing element 30 to thus confine the sealing element 30 againstextrusion in either longitudinal direction with respect to the pipe P.

When it is desired to retract the blowout preventer B from its sealingposition (FIG. 2) to its open or retracted position (FIG. 1) thepressure in the recess 12a is relieved through the relief line b orother suitable means so that the annular piston 14 returns to its normalundistorted condition by its own inherent resiliency or other suitablemeans. Likewise, the sealing element returns to its normal undistortedposition of FIG. 1, carrying with it the segments 36 and 36, whichthrough connectors 40 and pins 42 carry with them the segments 35 and35', respectively, so that they move to their fully open position (FIGS.1 and 3).

In the modified form of this invention illustrated in FIGS. 7-9, ablowout preventer 3-1 of the ram type is illustrated, utilizing the sameanti-extrusion means M and M and modified only to accommodate thesemicylindrical configuration of the rams R of the blowout preventer B-lrather than annular shape of the preventer B.

The blowout preventer B-l has a housing H-l of any suitable constructionwhich is adapted to be connected in a stack of blowout preventers or ina string of well casing or pipe in the conventional manner. Thus, thehousing H-l has a longitudinal central bore therethrough for the passageof the pipe P or other well tools in the known manner. The housing H-lalso has upper and lower flanges 51 with bolt openings 51a or othersuitable means for connecting the preventer 13-1 in the stack of thepreventers or in the well casing. The rams R are adapted to fit withinlateral recesses 50a in the housing H which communicate with thelongitudinal bore 50 in the known manner.

A conventional head or bonnet 52 is connected to each side of thehousing H, and each of such heads or bonnets 52 has a recess 52a (one ofwhich is shown in FIG. 7) and each of which is aligned with the lateralopenings 50a in the housing H-l, so as to form a continuation thereof.The rams R are received in their respective recesses 52a when they arein the retracted position (FIG. 8). A piston rod 54 extends through asuitable seal 52b in the bonnet 52 and is connected to a piston 56disposed in the cylinder 57 in the known manner. The cylinder 57 isclosed by a cap 58 having a fluid inlet line 58a therewith for theintroduction of hydraulic fluid or other fluid for operating the piston56. Another fluid line 520 is provided for communicating with theopposite side of the piston 56 for introducing hydraulic fluid or otherfluid to move the piston 56 to the right or outwardly from the positionshown in FIG. 7. It will be understood that the piston 56 is merelyexemplary of any suitable power means for moving the rams R, and asimilar power means is provided for each of the rams R, although onlythe piston 56 is illustrated for the right-hand ram R in FIG. 7.

To facilitate the description, the details of only one of the rams Rwill be described hereinafter, and only wnen it is necessary to show theinteraction of the two rams will the other ram be specificallyidentified. However, it will be understood that the two rams R arepreferably made in the same manner and bear like numerals and/or lettersfor identification purposes.

Thus, each ram R has a ram carrier 60 which is connected to the pistonrod or stem 54 preferably in the conventional releasable manner,utilizing a button 54a on the rod 54 fitting into a suitable slot in theram carrier 60. The ram carrier 60 is preferably formed of steel orother relatively rigid material and is substantially semi-cylindrical incross-sectional shape (FIG. 8). The ram carrier 60 is provided with aninternal recess or surface 60a which is likewise substantiallysemicylindrical in cross-sectional shape and which is adapted to receivea seal element 61 formed or rubber or other suitable resilient materialand preferably having an external convex surface 61a which substantiallyconforms with the internal surface of the recess 60a (FIG. 8). Sideanti-extrusion plates 62 formed of steel or other metal are disposed soas to engage the inside surface of an inwardly extending lip 50b on thehousing H-L'During movement of the carrier 60 from the position of FIG.8 to the stop position of FIG. 7, there is a sliding movement betweenthe carrier 60 and the side plates 62 as the seal element 61 deforms andurges the semi-cylindrical sealing member S into sealing contact withthe pipe P.

The seal member 61 is confined at its upper end between the ram carrier60 and an upper ram confining and alignment plate 64 which is alsopreferably semicylindrical (FIG. 1) which plate 64 is secured to thecarrier 60 by one or more cap screws 66 or other suitable securingmeans. It is to be noted that the upper surface 60b of the ram carrier60 engages and slides relative to the upper surface of the recess 50aand the recess 52a. The upper surface 61b of the seal member 61 engagesand seals with the upper surface of the recess 50a.

Each ram R also has a lower ram confining and alignment plate whichpreferably extends for the full depth of the ram and which is providedwith a shoulder 65a or other suitable engaging means for enabling thecarrier 60 to retract the plate 65 outwardly therewith but permittinginward movement of the carrier 60 relative to the plate 65 after inwardmovement of the plate 65 is stopped by engagement with the oppositeplate 65 on the other ram R.

It is to be noted that the vertical or longitudinal area between theupper alignment plate 64 and the lower alignment plate 65, and inwardlyof the seal member 61, forms a pocket or recess which is generallysemicylindrical for receiving the parts of the ram R which are normallythe primary replaceable parts. Such parts may be preassembled andinserted initially into position as will be more evident hereinafter.

Also, replacement assemblies including such parts may be used whennecessary.

Such replaceable assembly of the ram R includes the yieldable sealingelement or member S formed of rubber or other similar resilientyieldable material. The upper anti-extrusion means M shown in FIGS. 7-9is provided above the sealing element S for each of the rams R andlikewise, the lower anti-extrusion means M is provided below the sealingelement S for each of the rams R.

As best seen in FIG. 9, the anti-extrusion means M for each ram Rincludes the segments or anti-extrusion members 35 and 36 which aredisposed in the two layers in the same manner as described heretofore inconnection with FIGS. 1-6, the only difference being that the segments35 are arranged in a semi-circular or semi-cylindrical form when usedwith the rams R of FIGS. 7 and 8. It should also be noted that the endsegments in the upper anti-extrusion means M for each ram R are modifiedso as to be only partial segments as compared to the other segments 35so that the identical to that heretofore described for the antiextrusionmeans M, except that they are upside down with respect to each other asis evident from FIG. 7.

In the operation or use of the form of the invention shown in FIGS. 7-9,the rams R are operated in the conventional manner, utilizing hydraulicpressure supplied to the line 58a for moving the piston 56 for each ramR inwardly from the open or retracted position (FIG. 8) to the inner orsealing position (FIG. 7). When the rams contact each other at theradial surfaces 64a and 65a, the inward momvement of the confiningplates 64 and 65 is prevented, but the carrier can still exert an inwardradial force on the seal member 61 and the sealing element S for each ofthe rams R. Such distortion of the sealing member S continues until itis in full sealing contact with the external surface of the pipe P.

During the inward radial movement or distortion of the sealing elementS, the segments 36 and 36 are moved with the material of the sealingelement S radially inwardly so as to constantly maintain a metallicbarrier to prevent longitudinal extrusion of the flexible material ofthe sealing element S. The extrusion members 35 move with the elements Sby reason of the connectors 40 and likewise the segments 35 move withthe segments 36 by reason of the connectors 40 so as to avoid anyextrusion of the rubber or other material of the sealing element Sbetween the segments 36 and 36, respectively. Ultimately, the segmentsof the extrusion means M and M also contact the external surface of thepipe P and thus block longitudinal extrusion of the sealing element S ineither longitudinal direction relative to the pipe P. Upon a release ofthe pressure acting on the piston 56 and the application of pressure tomove same outwardly for each of the rams R, the rams R are retracted andare moved to the position of FIG. 8 so as to provide the full open borecorresponding to the bore 50 of the housing H-l in the known manner.

Instead of the dished out or concave surface 30a, the shape of thesurface 30a or other portions of the sealing member 30 may be modified,or recesses or the like in the member 30 may be provided, the purpose ofwhich is to compensate, or partially compensate, for the smaller volumeof the space available for the rubber of the member 30 when it is in itssealing position (FIG. 2) as compared to the volume of the spaceavailable for such member 30 in its retracted position (FIG. I).

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape, and materials as well as in the details of the illustratedconstruction may be made without departing from the spirit of theinvention.

I claim:

1. A blowout preventer adapted to seal with a pipe or other object in awell bore or to close same in the absence of any object in the wellbore, comprising:

a resilient sealing member having an inner curved surface adapted toengage a pipe or the like in a well bore;

means for urging said sealing member radially inwardly for effecting aseal with a pipe or the like in a well bore or with itself for closing awell bore; and

first anti-extrusion means mounted with said sealing member and movableradially therewith in response to radial inward movement of said sealingmember for preventing extrustion of the sealing member longitudinallywhen fluid pressure acts on said sealing member, said firstanti-extrusion means comprising:

a first set of anti-extrusion members circumferentially disposed withrespect to each other and mounted for radial movement;

a second set of anti-extrusion members, mounted below said first set andstaggered circumferentially with respect to said anti-extrusion membersin said first set to close radial spaces therebetween; and

separate connector means connecting said first set of anti-extrusionmembers to said second set for effecting radial movement thereoftogether.

2. The blowout preventer set forth in claim 1,

wherein:

said sealing member is substantially semi-cylindrical and is adapted tobe mounted as a part of a blowout preventer ram.

3. The blowout preventer set forth in claim 1,

wherein said sealing member is annular.

4. The blowout preventer set forth in claim I, including:

second anti-extrusion means mounted with said sealing member on theopposite side longitudinally of said sealing member from said firstanti-extrusion means and movable radially relative to said sealingmember in response to radial inward movement of said sealing member forinhibiting extrusion of the sealing member longitudinally when fluidpressure acts on said sealing member from either longitudinal direction.

5. The structure set forth in claim 4, wherein said secondanti-extrusion means includes:

a first set of anti-extrusion members circumferentially disposed withrespect to each other and mounted for radial movement;

a second set of anti-extrusion members mounted below said first set andstaggered circumferentially with respect to said anti-extrusion membersin said first set to close radial spaces therebetween; and

said anti-extrusion members in such first and second sets havingoverlapping surfaces, the extent of overlap of which increases as theanti-extrusion members move radially inwardly.

6. The structure set forth in claim 5, wherein:

each of said anti-extrusion members in said second set of anti-extrusionmembers of said second antiextrusion means is bonded to said sealingmember and is movable therewith; and

connector means connecting said first set of antiextrusion members insaid second anti-extrusion means to said second set for effecting radialmovement thereof together.

7. The structure set forth in claim 6, wherein said connector meansincludes:

a connector plate secured to each of said antiextrusion members in saidsecond set for movement therewith; and

circumferential slide connection means connecting said connector plateto each of two of the antiextrusion members in said first set above theantiextrusion member in said second set to which said plate is securedfor thereby providing limited circumferential movement of said connectedmembers relative to each other as they move together radially.

8. The structure set forth in claim 1, wherein:

said anti-extrusion members in said first and second sets havingoverlapping surfaces, the extent of overlap of which increases as theanti-extrusion members move radially inwardly.

9. The structure set forth in claim 8, wherein:

each of said anti-extrusion members in said second set of anti-extrusionmembers of said first antiextrusion means is bonded to said sealingmember and is movable therewith.

10. The structure set forth in claim 1 wherein said separate connectormeans includes:

a connector plate secured to each of said antiextrusion members in saidsecond set for movement therewith; and

circumferential slide connection means connecting said connector plateto each of two of the antiextrusion members in said first set above theantiextrusion member in said second set to which said plate is securedfor thereby providing limited circumferential movement of said connectedmembers relative to each other as they move together radially.

11. The structure set forth in claim 10, wherein said circumferentialslide connection means includes:

a circumferential slot in each said connector plate for each of said twoanti-extrusion members in said first set; and

a pin with each of said two anti-extrusion members in said first setextending through said slot and having a head thereon to force theanti-extrusion members in said first set to move radially with theantiextrusion members in said second set while permitting relativecircumferential movement during such radial movement.

1. A blowout preventer adapted to seal with a pipe or other object in awell bore or to close same in the absence of any object in the wellbore, comprising: a resilient sealing member having an inner curvedsurface adapted to engage a pipe or the like in a well bore; means forurging said sealing member radially inwardly for effecting a seal with apipe or the like in a well bore or with itself for closing a well bore;and first anti-extrusion means mounted with said sealing member andmovable radially therewith in response to radial inward movement of saidsealing member for preventing extrusion of the sealing memberlongitudinally when fluid pressure acts on said sealing member, saidfirst anti-extrusion means comprising: a first set of anti-extrusionmembers circumferentially disposed with respect to each other andmounted for radial movement; a second set of anti-extrusion members,mounted below said first set and staggered circumferentially withrespect to said antiextrusion members in said first set to close radialspaces therebetween; and separate connector means connecting said firstset of antiextrusion members to said second set for effecting radialmovement thereof together.
 2. The blowout preventer set forth in claim1, wherein: said sealing member is substantially semi-cylindrical and isadapted to be mounted as a part of a blowout preventer ram.
 3. Theblowout preventer set forth in claim 1, wherein said sealing member isannular.
 4. The blowout preventer set forth in claim 1, including:second anti-extrusion means mounted with said sealing member on theopposite side longitudinally of said sealing member from said firstanti-extrusion means and movable radially relative to said sealingmember in response to radial inward movement of said sealing member forinhibiting extrusion of the sealing member longitudinally when fluidpressure acts on said sealing member from either longitudinal direction.5. The structure set forth in claim 4, wherein said secondanti-extrusion means includes: a first set of anti-extrusion memberscircumferentially disposed with respect to each other and mounted forradial movement; a second set of anti-extrusion members mounted belowsaid first set and staggered circumferentially with respect to saidanti-extrusion members in said first set to close radial spacestherebetween; and said anti-extrusion members in such first and secondsets having overlapping surfaces, the extent of overlap of whichincreases as the anti-extrusion members move radially inwardly.
 6. Thestructure set forth in claim 5, wherein: each of said anti-extrusionmembers in said second set of anti-extrusion members of said secondanti-extrusion means is bonded to said sealing member and is movabletherewith; and connector means connecting said first set ofanti-extrusion members in said second anti-extrusion means to saidsecond set for effecting radial movement thereof together.
 7. Thestructure seT forth in claim 6, wherein said connector means includes: aconnector plate secured to each of said anti-extrusion members in saidsecond set for movement therewith; and circumferential slide connectionmeans connecting said connector plate to each of two of theanti-extrusion members in said first set above the anti-extrusion memberin said second set to which said plate is secured for thereby providinglimited circumferential movement of said connected members relative toeach other as they move together radially.
 8. The structure set forth inclaim 1, wherein: said anti-extrusion members in said first and secondsets having overlapping surfaces, the extent of overlap of whichincreases as the anti-extrusion members move radially inwardly.
 9. Thestructure set forth in claim 8, wherein: each of said anti-extrusionmembers in said second set of anti-extrusion members of said firstanti-extrusion means is bonded to said sealing member and is movabletherewith.
 10. The structure set forth in claim 1, wherein said separateconnector means includes: a connector plate secured to each of saidanti-extrusion members in said second set for movement therewith; andcircumferential slide connection means connecting said connector plateto each of two of the anti-extrusion members in said first set above theanti-extrusion member in said second set to which said plate is securedfor thereby providing limited circumferential movement of said connectedmembers relative to each other as they move together radially.
 11. Thestructure set forth in claim 10, wherein said circumferential slideconnection means includes: a circumferential slot in each said connectorplate for each of said two anti-extrusion members in said first set; anda pin with each of said two anti-extrusion members in said first setextending through said slot and having a head thereon to force theanti-extrusion members in said first set to move radially with theanti-extrusion members in said second set while permitting relativecircumferential movement during such radial movement.